Identifying direct subcortical pathways of the amygdala within the human auditory system using diffusion weighted imaging tractography

Poster Session B - Sunday, April 14, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Emmanouela Kosteletou Kassotaki^1,2 (emmakosteletou@ub.edu), Martina Trisia Cinca-Tomás^1,2, Federico Varriano³, Guadalupe Soria^2,3,4, Alberto Prats-Galino^3,4, Judith Domínguez-Borrás^1,2; ¹Brainlab – Cognitive Neuroscience Research Group, Department of Clinical Psychology and Psychobiology, University of Barcelona, ²Institute of Neurosciences, University of Barcelona, Spain, ³Laboratory of Surgical Neuroanatomy, Faculty of Medicine, University of Barcelona, Barcelona, Spain, ⁴Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain

Quick and efficient detection of threat is critical for survival. To serve this ability, a visual subcortical pathway, is believed to function in humans as a shortcut to the amygdala (a key structure for threat detection), with direct neural projections from the retina, superior colliculus and the pulvinar of the thalamus. Similarly, evidence from non-human animals suggest the existence of a homologous subcortical pathway in audition, but this pathway remains unknown in humans. To address this question, we applied probabilistic streamline tractography and Fixel Based Analysis to diffusion-weighted images obtained from the Human Connectome Project, reconstructed candidate auditory subcortical pathways and correlated their metrics with behavioral data available. Similarly, we examined the existence of an additional subcortical output pathway from the amygdala to the inferior colliculus, previously only described in bats. Our findings suggest the existence of white matter tracks directly projecting to the amygdala from the medial geniculate body of the thalamus and the auditory and audiovisual portions of the pulvinar (i.e. anterior and medial) showing left-right asymmetries. Interestingly, individuals with greater fiber density and number of streamlines in these pathways show a better hearing ability in noise and stronger feelings of fear and anxiety, respectively. These results point to the existence of a human auditory pathway for fast threat detection that may be homologous to that in the visual system. Finally, our evidence suggests the existence of a subcortical pathway connecting the amygdala with the inferior colliculus in humans, which may impose emotional content into sensory stimulus processing.

Topic Area: EMOTION & SOCIAL: Emotional responding